Weather extremes are thrashing the world, and it’s just a taste of what’s to come

Natural disasters and extreme weather are thrashing the northern hemisphere as temperature records rapidly topple. Floods are overwhelming parts of Asia and Europe, fires are ravaging the US, sea surface temperatures off Europe are the hottest on record and the global average temperature has been at a record high four times in the past week.

Drought is sapping northern parts of China and heatwaves are paralysing cities at the same time deadly floods displace thousands in the south. It’s just a taste of what’s to come as climate change worsens.

Floods

The ingredients for the catastrophic weather events in the northern hemisphere have been brewing in global oceans for months. In the lead-up to Earth’s hottest week in recorded history, between July 3 and 9 this year, 40 per cent of the world’s oceans were stewing through severe marine heatwaves.

“A big part of the fact that we’ve got these records occurring is because the oceans are so warm,” said marine heatwave expert Associate Professor Alex Sen Gupta from UNSW’s Climate Change Research Centre. “It means it’s very likely that this is going to be the warmest year on record.”

Much of the North Atlantic suffered the most extreme marine heatwaves in history. National Oceanic and Atmospheric Administration called a Category 5 (beyond extreme) heatwave in waters west of Ireland as temperatures climbed 5 degrees above the June average.

The record marine heat in the Atlantic spurred the formation of Tropical Storm Bret, the most eastward ever tropical storm this early in the year. Bret churned westward and swept through the Caribbean, damaging water infrastructure in Barbados and shuttering schools in St Lucia.

The ocean heatwaves have a high chance of holding strong for months, potentially contributing to bursts of damaging rain or intensifying heatwaves in Britain and Europe; one of either extremes. The warm water will mix deeper down into the ocean and have global effects – including on Arctic sea ice – for months.

The National Oceanic and Atmospheric Administration (NOAA) predicts that by September, 50 per cent of the world’s oceans could be experiencing marine heatwaves. The normal global rate is 10 per cent.

Weatherzone meteorologist Yoska Hernandez said the sea surface temperatures off Australia are the warmest on record, about 0.3 to 0.5 degrees warmer than last year.

Warm oceans are particularly concerning because they increase moisture in the atmosphere, which can lead to more intense rain events. In the last two weeks, major floods have swept across the US, China, Japan, Europe and Pakistan. Hernandez said the drivers behind the rain events are all separate, but all occurred in the context of climate change.

For example, the Pakistan event has been the result of seasonal monsoonal rains, with as much as six months’ of rain falling in 18 hours over some cities.

The floods in the north of America have been driven by an intense front moving over the region, dumping a lot of rain. There’s a lot of moisture in the atmosphere driven by the warming ocean temperatures.

In Spain, a large thunderstorm has resulted in flash flooding across Zaragoza in the country’s northeast – with about 64mm falling over some parts in a few hours. This is almost the average rainfall during summer for the country.

Heat

Last week, there were four days in which Earth’s average temperature reached record highs. The global average temperature hit 17.2 degrees on Thursday, July 6, surpassing the 17.18-degree record set on July 4 and equalled on July 5, according to data from the University of Maine’s Climate Reanalyser. The previous record of 17.01 degrees was set on Monday, July 3.

The data relies on satellite information and computer simulations to measure the world’s condition. It is, however, worth noting NOAA said it could not yet validate the data but that the agency recognised the warm period was due to climate change.

“Combined with El Niño and hot summer conditions, we’re seeing record warm surface temperatures being recorded at many locations across the globe,” the agency said in a statement last week.

The World Meteorological Organisation, a specialised agency of the UN, declared the El Niño event last week. It’s one of the most important drivers of unusual weather over the entire globe. In the southern hemisphere, El Niño tends to have a drying effect, but in the northern hemisphere, it can increase rainfall.

For most of Australia, El Niño brings dry weather, increasing bushfire risk. But in other parts of the world an El Niño event leads to wetter conditions, as in southern America.

The Bureau of Meteorology is yet to formally declare an El Niño event, but is expected to do so in the coming weeks. The agency has different criteria than other international weather agencies.

Sen Gupta said it was unusual so many weather events associated with El Niño, including fires and marine heatwaves, were striking before the weather system had even formed (the system has a 90 per cent chance of fully taking hold in the second half of the year).

Countries including Australia were warned to prepare for bad fire seasons. North America is currently in the midst of its most catastrophic fire season ever, which has seen nearly 4000 fires tear across Canada. Smoke spewed from the incineration of 9.5 million hectares and caused the worst air pollution in large swathes of the US in recorded history, draping cities such as New York in orange clouds of smog last month.

Last week in Beijing, as heat records topple across Asia, the government ordered a pause in outdoor work as the city hit a 10-day streak of days above 35 degrees, at the same time floods carried off cars and destroyed buildings, killing at least a dozen people and displaced thousands more in central and southern China.

Pinpointing the effect of climate change on one weather event is a difficult science, but a network of global researchers from the World Weather Attribution zeroed in on a four-day heatwave that killed 13 people. Using peer-reviewed analysis techniques and datasets, they concluded that human-induced climate change made the deadly heat 30 times more likely. (Another 96 people died from heat-related conditions in India in June.)

Have we reached the tipping point?

It’s a question we have to keep coming back to as records continually topple.

Dr Nandini Ramesh, a senior research scientist at CSIRO Data61, said it’s important to understand what a tipping point is.

“A tipping point is when you push something until it can’t be undone and it exacerbates further warming. An example is the west Antarctic ice sheet collapsing which would cause irreversible effects on ocean circulation and climate,” she said.

But Ramesh said currently we’re seeing gradual changes in our climate as greenhouse gas emissions increase temperatures. As this continues, we’ll see heavier rainfall events – like what has been seen in the US, Spain and Pakistan – as well as increasing heatwaves.

Sen Gupta said the Great Barrier Reef was an example of an approaching tipping point as successive devastating marine heatwaves risk bleaching the entire ecosystem into oblivion. Researchers are debating the current marine heatwave categorisation system as the heatwaves increase in intensity and frequency – a trend he attributed almost entirely to human-induced climate change.

“The ocean will [have] almost constant marine heat waves if we keep on pumping carbon dioxide into the atmosphere. We have to continually update what we class as a marine heatwave or, or go to more extreme definitions.”

More than 61,000 people died because of last year’s brutal summer heat waves across Europe, according to a study published Monday in the journal Nature Medicine. The findings suggest that two decades of efforts in Europe to adapt to a hotter world have failed to keep up with the pace of global warming.

Extreme heat had been expected that summer based on how much the planet had warmed overall in the past decade, the report notes. But this trend is likely to continue in the coming decades as climate change worsens.

“Having a warmer atmosphere makes both intense rain and heat waves worse,” Ramesh said. “It will push us into temperatures that are more dangerous to the human body.”

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